471959 Regulating the Timing and Sequence of Pro- and Anti-Inflammatory Cytokine Deliveries from Magnetically Responsive Biomaterials for Use in Wound Healing Applications
Our biomaterial system was composed of two-compartments: (1) a porous gelatin outer compartment designed to recruit macrophages and establish an initial pro-inflammatory (M1) phenotype, and (2) a magnetically responsive alginate inner compartment which was designed to deliver IL-4 and/or IL-10 when magnetically triggered to shift the response to anti-inflammatory by promoting (M2) phenotype. This magnetically responsive inner compartment was made by casting 7 wt% Fe3O4in 1 wt% alginate with 2.5 mM adipic acid dihydrazide (AAD) crosslinking in the presence of a magnet to generate biphasic gels. These biphasic gels were then swollen in water, frozen at -20°C, and lyophilized to generate porous, magnetically compressible biphasic gel structures. Gelatin outer compartments were loaded with 1000 ng of IFN-γ and designed to diffusively release IFN-γ early on. Magnetically deformable inner compartment gels were loaded within 100-1000 ng of IL-4 or IL-10 and were designed to deliver these anti-inflammatory proteins to macrophages that were recruited to the outer compartment at a time dictated by the application of the magnetic stimuli. A pulsatile 5 kGauss graded magnetic field was used in these experiments and applied at 1.5 Hz. Validation of these protein delivery profiles over time were quantified for IL-4, IL-10, and IFN-γ using ELISA.
We have demonstrated this system’s ability to initially release a pro-inflammatory cytokine (IFN-γ). We have found that more than 95% of the loaded IFN-γ was released from the outer compartment in the first 6 hours. We have also shown the ability to retain anti-inflammatory cytokines (IL-4 and IL-10) for several days and magnetically trigger their release from the inner compartment. Furthermore, we were able to magnetically control the timing and rate of these deliveries. For example, we showed that when we load 1000 ng of IL-4 in the inner compartment, we were able to retain IL-4 in the gel for 4 days with low release rates prior to magnetic stimulation (29.6 ± 3.3 ng/day for 4 days) and magnetically trigger enhanced release rates on day 4 (345.8 ± 103.29 ng/day over 4 hours). Using gels loaded with 500 ng of IL-10, we again demonstrated excellent retention for 3 days prior to magnetic stimulation (0.17 ± 0.04 ng/day for 3 days) and magnetically enhanced release rates on day 3 (6.99 ± 4.24 ng/day over 3 hours). The timing of IL-10 delivery could be stimulated on day 5 instead of day 3. In this case, IL-10 was retained at a low release rate prior to magnetic stimulation (0.11 ± 0.04 ng/day for 5 days) and magnetically released at enhanced rates on day 5 (3.67 ± 0.776 ng/day for 4 hours). Finally, the rate of IL-4 release could be controlled by using different magnetic stimulation regiments. For example, the release rate of IL-4 when magnetically stimulated at 1.5 Hz for 1 hour every 12 hours for over days was only 20.23 ±7.33 ng/day whereas continuous magnetic stimulation at 1.5 Hz for 4 hours resulted in a much higher release rate (345.85 ±103.29 ng/day). We believe that this biomaterial system will be highly useful for understanding how the timing and sequence of cytokine deliveries impact wound healing outcome.
Keywords: Wound healing, Macrophages, Cytokine delivery, Biomaterial, Magnetic stimulation.
- Sen, Chandan K. et al. “Human Skin Wounds: A Major and Snowballing Threat to Public Health and the Economy.” Wound Repair and Regeneration 17.6 (2009): 763–771.
- Frykberg, Robert G., and Jaminelli Banks. “Challenges in the Treatment of Chronic Wounds.” Advances in Wound Care 4.9 (2015): 560–582.